No specific actions have been identified that trigger or force any one specific spell to be dropped over another one.
Loremaster has three minions, Ice minion, Life minion, and Storm Minion. Ice casts weakness on you and your teammates. Life heals itself and everyone on its team, while the storm minion casts traps on you and your teammates. Many players will take out the ice minion first, followed by the life and storm minion, and finally Loremaster herself. And if you and your teammates have powerful attack all opponent spells like tempest, deer knight, forest lord, etc; you can simply one shot kill everything with enough pips, blades, and traps.
The best suggestion I can offer, when you intend to farm for one or more spells, is to also spend time gathering the required crafting components and regents, this way, when Loremaster gives you one spell, you can use most of the same spell crafting regents on another Loremaster spell.
The loremaster is a boss located in Dragonspyre (the Atheneum). To acess her, you will need to complete the Wizard City, Krokotopia, Marleybone, and Mooshu storylines. If you want to get there fast, stop doing Grizzeheim for now and continue on with storyline quests. Sarai Thunderstrider Magus
The Loremaster is found in Dragonspyre. You enter the Atheneum and there is an athame building. Inside there are sigils in which the loremaster is located in. You should take some higher level friends she is tough.
The Loremaster is in the library in the Atheneum in Dragonspyre. If you want to get to the Loremaster, don't worry about Grizzleheim and do the story line quests to get to Dragonspyre. And unless you're a higher level (I recommend probably 60+, others are different), I'd definitely go in with other people. Even though death is the best for soloing, you won't be able to do the Loremaster alone at your level.